LP - I folded down the top of the shirt where I had cut and overlocked, and using my sewing machine, stitched a 'tube' about 1 1/2 the width of the elastic, to make sure it fit through. Left a small gap to thread the elastic through using a safty pin, and stitched the elastic together - hope that makes sense?

This is especially great since at my house shirts tend to get tossed because of worn collars.... It looks so darn cute on you! If my slim hubby's shirts don't go round me they may make just the thing for my slim daughter or little granddaughter.....I've been sewing for over 50 years, why'n't I ever think of this before?